This application is based on and claims priority to Japanese Patent Application No. 10-303554 filed Oct. 26, 1998, the entire contents of which is hereby expressly incorporated by reference.
1. Field of the Invention
This invention relates generally to engine operation gauges and, more particularly, the invention relates to the encoding of various engine operation data for transmission over a signal line to a decoding receiver.
2. Description of the Related Art
Land and water vehicles typically display engine and/or vehicle operation information to the operator. Operation parameters such as, for example, vehicle speed, engine speed, engine temperature, and engine oil pressure are each typically displayed by a meter or gauge. A sensor senses the operation parameter and transmits the information to the gauge through a transmission medium such as a wire in the wiring harness of the vehicle. In typical applications, one wire carries information from each sensor to its associated gauge. Therefore, if there are numerous sensors and gauges, there will be numerous wires. A large number of wires is disadvantageous as the wires take up space, add weight, add more possible points of failure, and make fault detection more difficult.
For example, a watercraft that employ an internal combustion engine as a prime mover often uses a pulse generating mechanism to determine engine speed. Pulse signals commonly are generated by a pulsar coil on a flywheel magneto as a crankshaft of the engine rotates. These signals are sent to a remote display unit located near the operating controls of the watercraft.
The conventional engine speed display mechanism involves an engine speed sensor, which includes a pulse generating device (e.g., a pulsar coil), an engine speed display unit, and a wiring harness for connecting the speed sensor to the display unit. The watercraft also includes other sensors and controlled components disposed on or near the engine, e.g., a trim sensor and an electronic control unit (ECU). The wiring harness also connects these components to the display unit. The larger number of wires within the harness requires more time to install the engine and other components in the watercraft, thereby increasing manufacturing costs and complicating assembly of the watercraft.
The present invention involves systems and methods for collecting, encoding, transmitting, decoding, and displaying engine and vehicle operation information. In a preferred embodiment, a controller, such as, for example an engine control unit of an outboard boat motor, receives a plurality of engine and vehicle operation parameters from a plurality of sensors. The controller encodes the plurality of parameters in a single signal and transmits the encoded signal to a display unit over a signal line. The display unit decodes the encoded signal to extract the plurality of parameters and displays the extracted parameters to the vehicle operator.
In accordance with one aspect of the system, the controller encodes a first operation parameter as a pulse signal having a frequency related to the value of the first operation parameter. The controller also encodes a second operation parameter by adjusting the width of the pulse signal in relation to the value of the second operation parameter. The controller also encodes a third operation parameter by adjusting the height (i.e., amplitude) of the pulse signal in relation to the third operation parameter. A receiver (e.g., a display unit) decodes the pulse signal to extract the first, the second, and the third operation parameters based upon the frequency, the pulse width, and the pulse height, respectively, of the pulse signal. The three operation parameters can thus be advantageously transmitted through one signal line using the same pulse signal. Of course, other forms of time-varying periodic signals can be used as well with this system.
In accordance with another aspect of the system, a controller encodes an operation parameter as a pulse signal. The controller preferably scales the parameter to have a frequency in a first frequency range. The frequency is then offset by a constant value to produce an offset frequency occurring in a second frequency range. The second frequency range does not overlap with the first frequency range. The controller transmits the pulse signal at the offset frequency to a receiver. The receiver decodes the offset frequency to determine the value of the parameter.
In accordance with an additional aspect of the invention, the controller encodes two sets of vehicle operation information for alternate transmission over a signal line. The controller encodes a first set of engine operation parameters as a time-varying periodic signal within a first frequency range. The controller also encodes a second set of engine operation parameters as a time-varying periodic signal within a second frequency range. The controller alternately transmits the time-varying periodic signal of either the first or the second set of engine operation parameters over the signal line to a receiver (e.g., a display unit). The receiver determines whether the time-varying periodic signal is within the first or second frequency range and decodes the time-varying periodic signal accordingly to retrieve the first or second operation information.
Further aspects, features, and advantages of the present invention will become apparent from the detailed description of the preferred embodiments which follows.